,Learn what happens when stars explode,
Webb's increased size and sensitivity enable it to capture what has not been captured by other telescopes. “I think it's great to see that these supernovae can be recovered in the Webb data,” says Harvard University astronomer Edo Berger, who was not involved in the new research. The new data add to a growing record of exploding stars from various times in the universe's history. While the discovery of about 80 remote supernovae in a small part of the sky is significant, Berger says, “it's still a tiny fraction of all the supernovae being discovered by wide-field and shallow surveys, more than 10,000 supernovae per year.” But many of those supernovae are small and close to Earth. The importance of the Webb discoveries is in uncovering supernovae that represent much earlier times in the universe's history.
Peep into the past
To find more distant and therefore more ancient supernovae, the researchers compared multiple images taken by Webb over a period of a year. Astronomers looked for light sources that appeared or disappeared in the images, or what experts call transients. Not only did the researchers detect dozens of supernovae, but the nature of the light indicated that the supernovae exploded billions of years before our current moment.
Webb can detect supernovae thanks to a phenomenon called cosmological redshift. As light travels through space, its wavelengths are stretched, like taffy. The longer wavelengths of light fall into the infrared part of the spectrum — invisible to the naked eye, but visible to telescopes with the right equipment.
Different redshift characteristics correspond to different times in the universe's history, and the present day redshift is zero. The higher the redshift, the older the supernova. So, while a redshift of 2 indicates a supernova formed when the universe was about 3.3 billion years old, one of the newly detected supernovae has a redshift of 3.6 and was formed when the universe was about 1.8 billion years old. This makes the ancient supernova 12 billion years old, the oldest ever detected. The data provide a way to understand what the universe was like long before Earth existed. “The universe is about 14 billion years old, but these supernovae are from a time when the universe was just a few billion years old, which is the equivalent of being a teenager for humans,” Pearle says.